The present invention relates generally to electronic fuel injection systems and, more specifically, to an arrangement for producing a signal, for use in an electronic fuel injection system, which is representative of engine speed or RPM.
Various types of electronic fuel injection systems for internal combustion engines are known in the art. For example, reports in the "Motortechnische Zeitschrift" Vol. 34 (1973) No. 1 at page 7, and No. 4 at page 99, describe an electronic gasoline injection system that operates with an air volume flow meter. In this system a control device or system regulator is provided with signals which are derived from ignition pulses of the internal combustion engine and, thus, are a function of engine speed or RPM. On the other hand reports in the "Automobiltechnische Zeitschrift 73" (1971) No. 4, page 126; in "Bosch Technische Berichte 2", Vol. 3 (November, 1967) page 107, as well as in "Bosch Technische Berichte 3" Vol. 1 (November, 1969) page 3, describe a fuel injection system wherein engine speed-dependent signals are obtained by the addition of separate switch contacts on the engine distributor. With a fuel injection system in accordance with the literature passages first cited, the system control or regulator forms the quotient of the air volume measurement and the speed-dependent signal to obtain a signal proportional to the injection time; in contrast, in the injection system described in the latter-cited articles, the engine speed is only a corrective quantity.
In some motor vehicles provided with fuel injection systems of the above-described types unexplainable oscillations in the vehicle forward movement may occur under certain conditions of operation, e.g., when the vehicle is decelerated or when it is operated under partial load. However, this instability or tendency to oscillate does not occur in all vehicles of the same type and even occurs in varying degrees with the vehicles of the same type.